Method and system for stray light compensation

ABSTRACT

A method for stray light compensation is disclosed. The method comprising: acquiring a first image with a first imaging device covering a first field-of-view; acquiring a second image with a second imaging device covering a second field-of-view, wherein the second field-of-view is larger than the first field-of-view and wherein the first field-of-view is included in the second field-of-view; estimating stray light components in pixels of the first image from pixel data of pixels in the second image; and compensating for stray light in the first image by subtracting the estimated stray light components in pixels of the first image. Also, a system for stray light compensation is disclosed.

FIELD OF INVENTION

The present disclosure relates to stray light compensation, especiallystray light compensation in an image captured by a digital camera.

TECHNICAL BACKGROUND

Stray light is light in an optical system, such as a camera, which wasnot intended in the design. The stray light may originate from theintended source, but follow paths other than intended, or it may be froma source other than the intended source. Stray light may also bereferred to as lens flare. Lens flare occurs when light is scattered orflared in a lens arrangement. More precisely, light is scattered by thelens arrangement itself, for example through internal reflection andforward scattered from material imperfections in lenses of the lensarrangement. Lens flare can make the image look “washed out” by reducingcontrast and color saturation (adding light to dark image regions, andadding white to color saturated reaions, reducing their saturation).Lens flare is particularly caused by bright light sources. Hence, lensflare is a secondary effect that is widely distributed across the imageand typically not visible, although a does reduce signal-to-noise ratio,i.e., contrast, in the image. Accordingly, lens flare sets a workinglimit on a dynamic range in an image. Especially, a level of detail indarker portions of an image is limited by the lens flare.

There is a need for either reducing lens flare/stray light or by somemeans compensating for the lens flare/stray light being present in theimage.

SUMMARY

In view of the above, it is an object of the present disclosure toProviding compensation for the stray light being present in an image,especially in a digital image, would be beneficial. Additionally,mitigating, alleviating or eliminating one or more of theabove-identified deficiencies in the art and disadvantages singly or inany combination and solve at least the above-mentioned problem wouldalso be an improvement over current systems.

According to a first aspect, a method for stray light compensation isprovided. The method comprises: acquiring a first image with a firstimaging device covering a first field-of-view; acquiring a second imagewith a second imaging device covering a second field-of-view, whereinthe second field-of-view is larger than the first field-of-view andwherein the first field-of-view is included in the second field-of-view;estimating stray light components in pixels of the first image frompixel data of pixels in the second image; and compensating for straylight in the first image by subtracting the estimated stray lightcomponents in pixels of the first image. Thereby an improved first imagewith a reduction of stray light therein is provided. It is to be notedthat, even if the above discussed stray light compensation is notperfectly calibrated, the applied stray light compensation can still bevaluable since the stray light compensation provides for an improvedsignal-to-noise ratio in the first image. Hence, an increase in dynamicrange in the first image is provided. A possible effect of the presentstray light compensation is that it provides compensation for straylight originating from light sources outside the field-of-view of thefirst imaging device. This since such stray light components areestimated from the second image captured by the second imaging devicehaving a larger field-of-view than the first imaging device.

Estimating stray light components in pixels of the first image maycomprise: filtering the second image by a series of gaussian filtersforming a series of filtered second images; and linearly combining thefiltered second images forming a stray light image comprising straylight components from pixels in the first image.

Estimating stray light components in pixels of the first image maycomprise one or more of: determining a portion of the second imageoverlapping the first image; compensating for a difference in exposurebetween the second image and the first image; compensating fordifference in gain settings of the first imaging device and the secondimaging device; compensating for difference in pixel density between thesecond image and the first image; compensating for difference in viewangle between the second image and the first image; and compensating fordifference in aperture settings of the first and second imaging devices.

According to a second aspect, a non-transitory computer-readable storagemedium is provided. The non-transitory computer-readable storage mediumhaving stored thereon instructions for implementing the method accordingto the first aspect, when executed on a device having processingcapabilities.

According to a third aspect, a system for stray light compensation isprovided. The system comprises: a first imaging device covering a firstfield-of-view and being configured to acquire a first image; a secondimaging device covering a second field-of-view and being configured toacquire a second image, wherein the second field-of-view is larger thanthe first field-of-view and wherein the first field-of-view is includedin the second field-of-view; and circuitry configured to execute a straylight compensation function. The stray light compensation function beingconfigured to: estimate stray light components in pixels of the firstimage from pixel data of pixels in the second image; and compensate forstray light in the first image by subtracting the estimated stray lightcomponents in pixels of the first image.

A resolution of the second imaging device may be lower than a resolutionof the first imaging device.

The first and second imaging devices may be configured to capture thefirst and second images simultaneously.

The second imaging device may be configured to capture the second imageso that so that it is less saturated than the first image.

The second imaging device may comprise a fixed focal lens arrangement.

The second imaging device may be separate from the first imaging device.

According to a fourth aspect a video camera comprising the systemaccording to the third aspect is provided.

The above-mentioned features of the method, when applicable, apply tothe second, third or fourth aspects as well. In order to avoid unduerepetition, reference is made to the above.

A further scope of applicability of the present disclosure will becomeapparent from the detailed description given below. However, it shouldbe understood that the detailed description and specific examples, whileindicating preferred embodiments of the disclosure, are given by way ofillustration only, since various changes and modifications within thescope of the disclosure will become apparent to those skilled in the artfrom this detailed description.

Hence, it is to be understood that this disclosure is not limited to theparticular component parts of the system described or acts of themethods described as such system and method may vary. It is also to beunderstood that the terminology used herein is for purpose of describingparticular embodiments only, and is not intended to be limiting. It mustbe noted that, as used in the specification and the appended claim, thearticles “a,” “an,” “the,” and “said” are intended to mean that thereare one or more of the elements unless the context clearly dictatesotherwise. Thus, for example, reference to “a device” or “the device”may include several devices, and the like. Furthermore, the words“comprising”, “including”, “containing” and similar wordings does notexclude other elements or steps.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present disclosure will now bedescribed in more detail, with reference to appended figures. Thefigures should not be considered limiting; instead they are used forexplaining and understanding.

As illustrated in the figures, the sizes of layers and regions may beexaggerated for illustrative purposes and, thus, are provided toillustrate the general structures. Like reference numerals refer to likeelements throughout.

FIG. 1 illustrates a system for stray light compensation.

FIG. 2 is a schematic view from above of the system for stray lightcompensation looking at a scene.

FIG. 3 is a view of the scheme of FIG. 2 .

FIG. 4A is a view of the scene in FIG. 3 taken by a first imaging deviceof the system for stray light compensation before stray lightcompensation has been applied.

FIG. 4B is the same view as in FIG. 4A after stray light compensationhas been applied.

FIG. 5 is a block diagram of a method for stray light compensation.

DETAILED DESCRIPTION

The present disclosure will now be described more fully hereinafter withreference to the accompanying drawings, in which currently preferredembodiments of the disclosure are shown. This disclosure may, however,be embodied in many different forms and should not be construed aslimited to the embodiments set forth herein; rather, these embodimentsare provided for thoroughness and completeness, and to fully convey thescope of the disclosure to the skilled person.

A point spread function describes how an optical system depicts an idealpoint light source, i.e., the impulse response of the system. Amodulation transfer function is the Fourier transform of the pointspread function, i.e., the frequency response of the system. In the caseof an ideal lens (disregarding diffraction) the point spread functionwill be an infinitely narrow impulse, the Fourier transform of animpulse is 1 for all frequencies (i.e., all frequencies are unchanged bythe system). So, for a perfectly focused ideal lens, all the lightemanating from a single point in the scene will hit a single point onthe sensor. In reality, the point spread function never will beinfinitely narrow, some light will always hit neighboring pixels, asmall percentage of the light will even hit pixels far away. In thefrequency domain this can be seen as a gradual roll-off for higherfrequencies in the frequency response modulation transfer function. Fora real lens the point spread function varies depending on a lot offactors, e.g., the color of the light, the offset from the optical axisand the depth of field. Developing a lens will be a compromise betweencost and performance so that the lens can be optimized for handling“normal” scenes sufficiently well, i.e., the point spread function issupposed to be narrow enough to produce a good enough image in typicalsituations.

As the boundaries of high dynamic range imaging are pushed, therequirements on the lenses increase. A high dynamic range scenetypically contains at least some part that is significantly brighterthan the rest of the scene. Since the point spread function is notideal, some of the light from the bright areas will be spread toneighboring darker pixels resulting in an unwanted offset in thosepixels, reducing the contrast of the actual signal in dark areas. Evenif only a small fraction of the light from the bright areas is spread tothe dark areas, it might mean a significant contribution to these areas.This effect obviously becomes worse as the dynamic range, i.e., ratiobetween bright and dark, increases. This loss of contrast in dark areasneighboring bright areas can be seen as a first order limitation of thedynamic range of the lens, as it limits the ability to measure contrastin dark areas. In theory, if we have perfect knowledge of the pointspread function, it might be possible to reconstruct the ideal image bydoing a deconvolution, i.e., inverse convolution, using the point spreadfunction. However, even if a perfect subtraction of the stray lightoffset is managed, it would still suffer from the photon shot noiseintroduced by the stray light, i.e., due to photon shot noise there is aphysical limitation of the dynamic range possible to measure for a givenlens system. This can of course be circumvented by collecting morephotons, thereby reducing the temporal and/or spatial resolutioninstead.

If we had access to the ideal, i.e., stray light free, image it would befairly simple to estimate the stray light, it would just be a matter ofconvolving the ideal image with the point spread function.Unfortunately, there is no access to the ideal image, so instead anactual image approximation may be used. This might seem counterintuitiveat first, but considering:

-   -   psf—The point spread function    -   im_(ideal)—The ideal image without any stray light    -   im_(stray)—The stray light offset per pixel    -   im_(actual)—The image actually measured on the sensor

From the definitions above:

-   -   im_(actual)=im_(ideal)+im_(stray)

It would be ideal to calculate: im_(stray)=im_(ideal)*PSf-im_(ideal)

-   -   Alternatively, with the information that is available calculate:        im_(actual)*psf−im_(ideal)+im_(stray)*psf−im_(stray)=im_(stray)+im_(stray)*psf-im_(stray)=im_(stray)*psf≈im_(stray)

In other words, by approximating im_(ideal) by im_(actual) the straylight is overestimated a bit since it was erroneously assumed it toocontributes to the stray light, since it is convolved by the pointspread function. Note that this in theory can be improved iteratively byrefining the approximation of im_(ideal) in each iteration bysubtracting the previously estimated im_(stray) from im_(actual).

Additionally, the issue of performing a full resolution perfectpsf-convolution is extremely expensive and completely unrealistic.Instead, it is assumed that the point spread function can besufficiently well approximated by a sum of gaussian filters of varyingwidth, i.e., by filtering the actual image by a series of gaussianfilters that can reconstruct an approximation of the stray light as alinear combination of the filter results.

Hence, for a given lens arrangement, the point spread function whichdescribes how light is spread by the lens arrangement can be estimated.The point spread function can then be used to predict the amount ofstray light in an image captured using the lens arrangement. A limitingfactor when estimating the stray light this way is that only lightactually seen by the lens arrangement can be measured, light originatingfrom light sources outside of the field-of-view cannot be handled.

The present disclosure is based on the insight made by the inventorsthat an estimation of stray light in pixels of an image captured by afirst imaging device can be made from an image captured by anothersecond imaging device. The second imaging device is set to have a largerfield-of-view than the first imaging device. The field-of-view of thefirst imaging device is to be included in the field-of-view of thesecond imaging device. Further, typically, the second imaging device isset to capture images being less exposed than the images captured by thefirst imaging device. According to this, stray light components in animage captured by a first imaging device originating from light sourcesoutside the field-of-view of the first imaging device may be estimatedand compensated for. Hence, the disclosure is based on having a separatesecond imaging device with a wider field-of-field to acquire an image ofa larger portion of a scene covered by a first imaging device. Further,the separate second imaging device is preferably configured so that theimages captured thereby and being used for estimating stray light in animage captured by the first imaging device are without saturating lightsources. This may e.g., be safeguarded by using a different (typicallylower) exposure for images captured by the second imaging device thanfor images captured by the first imaging device. An image captured bythe second imaging device can then be used to estimate and subtractstray light from an image captured by the first imaging device. Thesecond imaging device may be a camera having a lower resolution than thefirst imaging device. This is since typically, the stray lightcomponents originating from light sources outside the field-of-view ofthe first imaging device are of spatially low frequency. Further, thesecond imaging device may even be a camera with fixed focal-lengthoptics.

FIG. 1 illustrates a system 100 for stray light compensation. The system100 comprises a first imaging device 110 and a second imaging device120. The first and second imaging devices 110, 120 are typicallyseparate imaging devices. The first and second imaging devices 110, 120may be arranged in one and the same housing, i.e., a camera devicehaving two imaging devices arranged therein. Alternatively, the firstand second imaging devices 110, 120 may be separate devices, i.e.,separate camera devices. Each imaging device 110, 120 comprises a lensarrangement 112, 122 and an image sensor 114, 124. That is, the firstand second imaging devices 110, 120 are typically digital cameras. Thelens arrangement 122 of the second imaging device 120 may be a fixedfocal lens arrangement. The lens arrangement 112 of the first imagingdevice 110 may be a zooming lens arrangement. The first imaging device110 covers a first field-of-view 111. The second imaging device 120covers a second field-of-view 121. The second field-of-view 121 islarger than the first field-of-view 111. The first field-of-view 111 isincluded in the second field-of-view 121. The first imaging device 110is configured to capture one or more first images. Hence, the firstimaging device 110 may be a still image camera or a video camera. Thesecond imaging device 110 is configured to capture one or more secondimages. Hence, the second imaging device 120 may be a still image cameraor a video camera. A resolution of the second imaging device 120 may belower than a resolution of the first imaging device 110.

The second field-of-view 121 is preferably of a size arranged so thatthe second imaging device 120 reproduce all light sources from whichlight reaches the first imaging device 110.

The second imaging device 120 is preferably configured to capture thesecond image so that pixels of the second image are less exposed thanpixels of the first image. Doing so facilitates capturing of a secondimage having less saturated pixels that the first image. Hence, thesecond image preferably has less saturated pixels than the first image.According to a non-limiting example, the second imaging device 120 isconfigured to capture the second image so that at least 99% of thepixels of the second image are unsaturated. Hence, it may be safeguardedthat a low number of pixels in the second image are saturated. Thisprovides for an improved stray light estimation. In order to achievethis, the second imaging device 120 is typically set to use a shorterexposure time than the first imaging device 110. Additionally, othersettings in the second imaging device 120 may be used for safeguardingthat a low number of pixels in the second image is saturated. Somenon-limiting examples are: using a less sensitive image sensor in thesecond imaging device 120; adjust the aperture of the second imagingdevice 120; and use an optical filter, such as a neutral density filter,in the second imaging device 120. The second imaging device 120 mayfurther be configured to capture the second image(s) as dual exposureimages. The second imaging device 120 may even be a black and whitecamera. This since the quality of the image(s) captured by the secondimaging device 120 is not of great importance as long as the images(s)captured thereby gives information pertaining to position andilluminance of light-sources outside the field of view of the firstimaging device 110.

According to one exemplifying embodiment, the first imaging device 110is a detailed-view imaging device and the second imaging device 120 is awide-angle imaging device. The detailed-view imaging device is coveringa detailed field-of-view and being configured to capture one or moredetailed-view images. The wide-angle imaging device covers a widefield-of-view and being configured to capture one or more wide-angleimages. The wide field-of-view is larger than the detailedfield-of-view. The detailed field-of-view is included in the widefield-of-view.

The system 100 further comprises circuitry 130. The circuitry 130 isconfigured to carry out overall control of functions and operations ofthe system 100. The circuitry 130 may include a processor 131, such as acentral processing unit (CPU), microcontroller, or microprocessor. Theprocessor 131 is configured to execute program code stored in a memory140, in order to carry out functions and operations of the system 100.

The memory 140 may be one or more of a buffer, a flash memory, a harddrive, a removable medium, a volatile memory, a non-volatile memory, arandom access memory (RAM), or another suitable device. In a typicalarrangement, the memory 140 may include a non-volatile memory for longterm data storage and a volatile memory that functions as system memoryfor the circuitry 130. The memory 140 may exchange data with thecircuitry 130 over a data bus. Accompanying control lines and an addressbus between the memory 140 and the circuitry 130 also may be present.

Functions and operations of the system 100 may be embodied in the formof executable logic routines (e.g., lines of code, software programs,etc.) that are stored on a non-transitory computer readable medium(e.g., the memory 140) of the system 100 and are executed by thecircuitry 130 (e.g., using the processor 131). Furthermore, thefunctions and operations of the system 100 may be a stand-alone softwareapplication or form a part of a software application that carries outadditional tasks related to the system 100. The described functions andoperations may be considered a method that the corresponding part of thesystem is configured to carry out. Also, while the described functionsand operations may be implemented in software, such functionality may aswell be carried out via dedicated hardware or firmware, or somecombination of hardware, firmware and/or software.

The circuitry 130 is configured to execute a stray light compensationfunction 142. The stray light compensation function 142 is configured toestimate stray light components in pixels of an image captured by thefirst imaging device 110, the image captured by the first imaging device110 will below be referred to as the first image. Such estimation is setto be made based on pixel data of pixels in an image captured by thesecond imaging device 120, the image captured by the second imagingdevice 120 will below be referred to as the second image. Moreprecisely, the estimation is made such that pixel data in a second imageis manipulated so that the pixel data indicative of stray lightcomponents in the first image originating from light sources outside thefield-of-view of the first imaging device 110 may be estimated for. Forexample, the second image may be manipulated by: filtering the secondimage by a series of gaussian filters forming a series of filteredsecond images; and linearly combining the filtered second images forminga stray light image comprising stray light components from pixels in thefirst image. The gaussian filters used may be empirically evaluated forthe system 100, i.e., by iteration. Hence, a selection of gaussianfilters to use can be found by calibration of the system 100.Accordingly, stray light components for pixels in the first image may beestimated from pixel values in the second image.

The estimation of stray light components in pixels of the first imagemay further depend on other factors. Some non-limiting examples are: anoverlap in field-of-view between the first and second image; exposuresof the first and second images; gain settings of the first and secondimaging devices 110, 120; pixel densities of the first and secondimages; view angles of the first and second imaging devices 110, 120;focus settings of the first and second imaging devices 110, 120; andaperture settings of the first and second imaging devices 110, 120.

All-in-all, stray light components for pixels in the first image may befound by applying a transfer function on pixel values of pixels in thesecond image; such a transfer function transferring how pixel values ofpixels in the second image influence stray light in the first image.That is, a transfer function may be applied on pixel values of pixels inthe second image transferring how stray light is affecting pixels in thefirst image. Such a transfer function may be depending on one or more ofthe factors discussed above. The transfer function may be empiricallyevaluated for the system 100 i.e., by iteration. Hence, the transferfunction to use for the system 100 can be found by calibration of thesystem 100.

The stray light compensation function 142 is further configured tocompensate for stray light in the first image by subtracting theestimated stray light components in pixels of the first image. Therebyan improved first image with a reduction of stray light therein isprovided.

Application of the system 100 for stray light compensation will now bediscussed in connection with FIGS. 2, 3, 4A and 4B. In FIG. 2 the system100 for stray light compensation looking at a scene comprising abuilding 200, a person 210 and a light source 220 is illustrated fromabove. In this specific example, the light source 220 is the sun. InFIG. 3 the scene of FIG. 2 is illustrated as depicted by the firstimaging device 110 having the first field-of-view 111 and by the secondimaging device 120 having the second field-of-view 121. The firstfield-of-view 111 is illustrated as covering the person 210 and aportion of the building 200. Important to notice is that the lightsource 220 is outside of the field-of-view 111 of the first imagingdevice 110. The second field-of-view 121 is illustrated as covering theperson 210 the building 200 and the light source 220. In FIG. 4A animage captured by the first imaging device 110 is illustrated beforestraylight compensation has been performed. In FIG. 4B the image of FIG.4A after straylight compensation has been performed is illustrated.

As will be discussed in connection with FIGS. 2, 3 and 4A the lightsource 220 outside of the field-of-view 111 of the first imaging device110 affects the image captured by the first imaging device 110. As isschematically illustrated by arrow 221 in FIG. 2 , light originatingfrom the light source 220 outside of the field-of-view 111 of the firstimaging device 110 will arrive at the first imaging device 110. Suchlight will affect image(s) captured by the first imaging device 110 asstray light/lens flare. An example of an image captured by the firstimaging device 110 is illustrated in FIG. 4A. In Fla. 4A stray lightoriginating from the light source 220 outside of the field-of-view 111of the first imaging device 110 is affecting the image mostly in theupper left portion of the image. The effect of the stray light isillustrated in FIG. 4A as dotted pattern. The dotted pattern illustratesthe noise introduced in the image due to stray light originating fromthe light source 220 outside of the field-of-view 111 of the firstimaging device 110. In FIG. 4B the image illustrated in FIG. 4A afterapplying the stray light compensation function 142 is illustrated. Asillustrated in FIG. 4B, after having compensated for stray light usingthe stray light compensation function 142, signal-to-noise ratio in theimage is enhanced. By the enhanced signal-to-noise ratio details in thestray light compensated image illustrated in FIG. 4B will be betterrepresented. This is exemplified in FIG. 4B by that the details of thebrick wall 205 on the building 220 is better represented as comparedwith FIG. 4A. The stray light compensation function 142 relay on imagedata from an image captured by the second imaging device 120 having afield-of-view 121 comprising the light source 220 outside of thefield-of-view 111 of the first imaging device 110. Hence, an estimationof stray light in pixels of an image captured by a first imaging device110 can be made from an image captured by the second imaging device 120.

In connection with FIG. 5 a method 500 for stray light compensation willbe discussed. Some of all the steps of the method 500 may be performedby the system 100 described above. However, it is equally realized thatsome or all of the steps of the method 500 may be performed by one ormore other devices having similar functionality. The method 500comprises the following steps. The steps may be performed in anysuitable order.

Acquiring S502 a first image with a first imaging device covering afirst field-of-view.

Acquiring S504 a second image with a second imaging device covering asecond field-of-view. The second field-of-view is larger than the firstfield-of-view. The first field-of-view is included in the secondfield-of-view.

Estimating S506 stray light components in pixels of the first image frompixel data of pixels in the second image. Estimating S506 stray lightcomponents in pixels of the first image may comprise: filtering thesecond image by a series of gaussian filters forming a series offiltered second images; and linearly combining the filtered secondimages forming a stray light image comprising stray light componentsfrom pixels in the first image.

The estimating S506 may further comprise one or more of: determining aportion of the second image overlapping the first image; compensatingfor a difference in exposure between the second image and the firstimage; compensating for difference in gain settings of the first imagingdevice and the second imaging device; compensating for difference inpixel density between the second image and the first image; compensatingfor difference in view angle between the second image and the firstimage; and compensating for difference in aperture settings of the firstand second imaging devices.

Compensating S508 for stray light in the first image by subtracting theestimated stray light components in pixels of the first image. Therebyan improved first image with a reduction of stray light therein isprovided.

The person skilled in the art realizes that the present disclosure by nomeans is limited to the preferred embodiments described above. On thecontrary, many modifications and variations are possible within thescope of the appended claims.

For example, the first and second imaging devices 110, 120 may beconfigured to capture the first and second images simultaneously. Inthis context simultaneously shall be understood as that the first andsecond images have an overlap in time when they are captured. It ishowever to be understood that one of the images may be captured using alonger exposure time than the other. Typically, the second image iscaptured using a shorter exposure time than the first image, this inorder to avoid overexposure of pixels in the second image. By thesimultaneous capturing of the first and second images it is providedthat the same lighting conditions are present in both images. Thisprovide for a better quality of the stray light compensation.

Additionally, variations to the disclosed embodiments can be understoodand effected by the skilled person in practicing the claimed disclosure,from a study of the drawings, the disclosure, and the appended claims.

1. A method for stray light compensation, the method comprising:acquiring a first image with a first imaging device covering a firstfield-of-view; acquiring a second image with a second imaging devicecovering a second field-of-view, wherein the second field-of-view islarger than the first field-of-view and wherein the first field-of-viewis included in the second field-of-view; estimating stray lightcomponents in pixels of the first image from pixel data of pixels in thesecond image; and compensating for stray light in the first image bysubtracting the estimated stray light components in pixels of the firstimage.
 2. The method according to claim 1, wherein estimating straylight components in pixels of the first image comprises: filtering thesecond image by a series of gaussian filters forming a series offiltered second images; and linearly combining the filtered secondimages forming a stray light image comprising stray light componentsfrom pixels in the first image.
 3. The method according to claim 1,wherein estimating stray light components in pixels of the first imagecomprises determining a portion of the second image overlapping thefirst image.
 4. The method according to claim 1, wherein estimatingstray light components in pixels of the first image comprisescompensating for a difference in exposure between the second image andthe first image.
 5. The method according to claim 1, wherein estimatingstray light components in pixels of the first image comprisescompensating for difference in gain settings of the first imaging deviceand the second imaging device.
 6. The method according to claim 1,wherein estimating stray light components in pixels of the first imagecomprises compensating for difference in pixel density between thesecond image and the first image.
 7. The method according to claim 1,wherein estimating stray light components in pixels of the first imagecomprises compensating for difference in view angle between the secondimage and the first image.
 8. A non-transitory computer-readable storagemedium having stored thereon instructions for implementing a method forstray light compensation, when executed on a device having processingcapabilities, the method comprising: acquiring a first image with afirst imaging device covering a first field-of-view; acquiring a secondimage with a second imaging device covering a second field-of-view,wherein the second field-of-view is larger than the first field-of-viewand wherein the first field-of-view is included in the secondfield-of-view; estimating stray light components in pixels of the firstimage from pixel data of pixels in the second image; and compensatingfor stray light in the first image by subtracting the estimated straylight components in pixels of the first image.
 9. A system for straylight compensation, the system comprising: a first imaging devicecovering a first field-of-view and being configured to acquire a firstimage; a second imaging device covering a second field-of-view and beingconfigured to acquire a second image, wherein the second field-of-viewis larger than the first field-of-view and wherein the firstfield-of-view is included in the second field-of-view; and circuitryconfigured to execute a stray light compensation function, the straylight compensation function being configured to: estimate stray lightcomponents in pixels of the first image from pixel data of pixels in thesecond image; and compensate for stray light in the first image bysubtracting the estimated stray light components in pixels of the firstimage.
 10. The system according to claim 9, wherein a resolution of thesecond imaging device is lower than a resolution of the first imagingdevice.
 11. The system according to claim 9, wherein the first andsecond imaging devices are configured to capture the first and secondimages simultaneously.
 12. The system according to claim 9, wherein thesecond imaging device is configured to capture the second image so thatit is less saturated than the first image.
 13. The system according toclaim 9, wherein the second imaging device comprises a fixed focal lensarrangement.
 14. A system according to claim 9, wherein the secondimaging device is separate from the first imaging device.
 15. A videocamera, including a system for stray light compensation, comprising: afirst imaging device covering a first field-of-view and being configuredto acquire a first image; a second imaging device covering a secondfield-of-view and being configured to acquire a second image, whereinthe second field-of-view is larger than the first field-of-view andwherein the first field-of-view is included in the second field-of-view;and circuitry configured to execute a stray light compensation function,the stray light compensation function being configured to: estimatestray light components in pixels of the first image from pixel data ofpixels in the second image; and compensate for stray light in the firstimage by subtracting the estimated stray light components in pixels ofthe first image.